Measurements of the blast pressures in Shots Dog, Easy, and George, together with earth-shock measurements on Shots Easy and George, gave new and important information concerning the magnitude and character of the blast wave near an atomic bomb. These experiments showed that secondary phenomena due presumably to thermal radiation and ion combination affect the pressure wave rather markedly near the source by introducing a large secondary pulse into the pressure-time curve and by causing the pressure wave near the ground to be nonshock in character. Both of these perturbations coalesce into a shock front at greater distances producing a blast wave of conventional shape. New techniques of measurement involving smoke-trail rockets, balloons, telemetering, and high-speed photography allowed the peak blast pressures in free air near the bomb to be obtained from which the explosive equivalent of one bomb (Easy) was determined. The equivalent blast energy was found to be approximately 50 per cent of the radiochemical energy for this case. By this is meant that only half the energy is required to produce the same blast wave at a great distance if released by a TNT explosion. Evaluation of the radiochemical kilotonnages from blast measurements was made by comparison with previous shots, giving kilotonnages 58, or Shots Dog, Easy, and George, respectively. Asymmetry of the explosion was investigated by measuring pressures on the ground along two radii. The results indicated a great asymmetry in the case investigated (Easy), which may be due to the presence of jets along the guy cables from the tower. Earth-shock measurements showed that the accelerations and frequencies of the motion were higher by a factor of 10 than predicted from small-scale experiments in soil and that the displacements were correspondingly smaller than predicted by a factor of 10.